Doc's Tip of the Evening -- Ball Movement at Surface Contact

Did you know that a tennis ball will slide across the surface of the court at impact when it is hit with a lot of underspin?
As the incoming rate of underspin decreases, a point will be reached where the ball begins to roll across the surface at the END of impact.
With an increasing rate of incoming topspin the ball will impact with a mixture of sliding and rolling.
At higher rates of topspin the ball will tend to roll more than slide.
Note that the ball will never fully roll upon impacting the surface of the court as today's players are not capable of generating fast enough spin rates. dd